The present invention relates to an improved linear vibrating device for vibrating a speaker diaphragm and a speaker equipped with such an improved linear vibrating device.
There have been known various small-sized vibrating devices suitable for use in speakers (loudspeakers) and particularly in planar speakers, as will be set forth below. In one type of planar speaker using an electrically-conductive actuator, as shown in FIG. 15, the actuator A is positioned in a center portion of a diaphragm P to drive or vibrate the diaphragm P. Because the electrically-conductive actuator A has a great weight and size, the actuator A would make it difficult to reduce the thickness of the planar speaker. In cases where a plurality of such electrically-conductive actuators are provided in the diaphragm, it is difficult to drive the individual actuators with no phase delay, and the necessary costs would greatly increase.
Small electrically-conductive actuators today used for information communications, such as telephone sounders and buzzers, can not appropriately drive the diaphragm of a planar speaker of an ordinary size, because they produce only small outputs although they are small enough in size.
Also known is a type of speaker using a piezoelectric film as a diaphragm vibrating source, which would however require high manufacturing costs. Further, the piezoelectric film would give rise to only small vibrating displacements due to its insufficient vibrating force in low frequencies.
There is known another type of planar speaker using printed coils. As schematically shown in FIGS. 16 and 17, electrically-conductive materials are printed on the diaphragm to provide a plurality of coils C. A plurality (a succession) of magnets M are positioned in opposed relation to the printed coils C, and the coils C and magnets M are enclosed by a common iron base B. The magnets M are arranged in such a manner that the different (N and S) magnetic poles thereof alternate along the longitudinal direction of the coils, and the coils C are formed in such a manner that they exhibit N and S magnetic poles alternately in correspondence with the alternate magnetic poles of the magnets. Specifically, as driving sound signals are input to the printed coils, the coils produce magnetic fields, so that attractive and repulsive forces between the coils and the magnets cause vibrations of the speaker diaphragm. However, because the diaphragm used in this type of planar speaker has a small vibrating area and has low rigidity, it can not produce sufficiently great outputs or outputs in low pitch ranges. Although the use of the printed coils on the diaphragm permits a reduction in the thickness of the planar speaker, it is necessary to wind every adjoining coils in opposite directions so as to correspond to the alternate N and S magnetic poles of the magnets, which would result in complicated wiring. Further, because this speaker yields driving force using leakage flux leaking out of the magnet fields produced between the adjoining coils and directed toward the corresponding coils, it achieves only a low driving efficiency, and the printed coils can not be positioned to overlap each other or inserted between the magnets. As a consequence, this conventional speaker can not produce great-enough outputs via the coils and magnets.
Therefore, with the speakers using the conventional diaphragm vibrating devices, it was difficult to reduce the speaker size and produce great outputs and good frequency characteristics.
In view of the foregoing, it is an object of the present invention to provide an improved speaker which is small in size and yet can produce great outputs and good frequency characteristics, as well as an improved vibrating device for use in such a speaker.
In order to accomplish the above-mentioned, the present invention provides a speaker which comprises: a diaphragm; and a linear vibrating device attached to a peripheral portion of the diaphragm for vibrating the diaphragm. The linear vibrating device includes a conductor line meandering, in a wave-like shape or configuration, along a first surface of the diaphragm, and a succession of magnets disposed in opposed relation to the conductor line. The magnets are disposed in regions surrounded by adjoining mountain portions and adjoining valley portions of the conductor line and are arranged in such a manner that the respective magnetic poles of each adjoining pair of the magnets are located close to the conductor line and have opposite (N and S) polarities.
In one embodiment, a plurality of the linear vibrating devices may be disposed along the peripheral portion of the diaphragm.
The speaker of the present invention may further comprise an auxiliary conductive line extending, in a wave-like shape, along a second surface of the diaphragm opposite to the linear vibrating device. The auxiliary conductive line corresponds in position to the conductor line of the linear vibrating device and is arranged to form magnetic poles of the same polarities as the magnetic poles of the conductor line of the linear vibrating device.
The speaker of the present invention may further comprise a succession of auxiliary magnets disposed on the other surface of the diaphragm opposite to the linear vibrating device in such a manner that the magnetic poles of the auxiliary magnets are opposed to the magnetic poles of the magnets of the linear vibrating device with the diaphragm interposed therebetween and have opposite polarities to the magnetic poles of the magnets of the linear vibrating device.
In one embodiment, a pair of the linear vibrating devices may be disposed on the opposite surfaces of the diaphragm so as to be opposed to each other with the diaphragm interposed therebetween.
The diaphragm may have a plurality of holes formed in the regions surrounded by the adjoining mountain portions and adjoining valley portions of the conductor line, and each of the holes may be formed as a through-hole or has a substance of high permeability inserted therein.
The diaphragm may have a plurality of holes formed in the regions surrounded by the adjoining mountain portions and adjoining valley portions of the conductor line, and the magnetic poles of the magnets may each be positioned within or in proximity to one of the holes. Alternatively, the speaker may further comprise a plurality of yokes each connected with one of the magnets, and the distal ends of the yokes, rather than the magnetic poles of the magnets, may each be positioned within or in proximity to one of the holes.
The conductor line may be provided on the diaphragm by plating or printing.
The speaker of the present invention may further comprise a piezoelectric vibrating device attached to the diaphragm along with the linear vibrating device.
According to another aspect of the present invention, there is provided a linear vibrating device which comprises: a conductor line meandering, in a wave-like shape, along a surface of a diaphragm; a succession of magnets disposed in opposed relation to the conductor line, the magnets being disposed in regions surrounded by adjoining mountain portions and adjoining valley portions of the conductor line and being arranged in such a manner that respective magnetic poles of each adjoining pair of the magnets are located close to the conductor line and have opposite polarities.